Part of any fibre enthusiast's hobby is an appreciation of yarn. Choose two yarns that you have either used, are in your stash or which you yearn after and capture what it is you love or loathe about them.
I love knitting/crocheting with almost any squishy extra-fine merino yarn but my absolute favourite is the now-sadly-discontinued Jaeger Extra Fine Merino DK. EFM is lovely to work with; it shows off textured stitches beautifully and never, ever pills in wear. I have a small hoard left - mainly in my favourite colours of purple, blackberry, grey. I can't quite bring myself to use any of the hoarded yarn yet but the anticipation of doing so is very enjoyable!
Top of the list in my Devil's Spawn category of yarns to avoid is Rowan Kidsilk Haze, narrowly beating any yarn containing bamboo (bamboo is slimy stuff; handling it makes me shudder with that chalk-on-a-blackboard feeling). I seem to be the only knitter on the planet who hates Kidsilk Haze. It's itchy to wear, horrible to work with and an absolute bugger to frog if you've made a mistake. Oh, and for what you get, it's ridiculously expensive.